Diisocyanate-induced occupational asthma (DA) is the most prevalent form of occupational asthma. Severe chronic disability due to DA can be prevented by early diagnosis and cessation of workplace exposure. However, there are no sensitive biomarkers of DA to facilitate an early diagnosis. In the past ten years, bronchoalveolar lavage and bronchial biopsy studies of workers with DA have defined an important pathogenetic role of airway inflammation. Previous studies have identified diisocyanate antigen-specific cellular responses in DA patients. These studies revealed that clinically confirmed DA is significantly associated with antigen-specific enhancement in PBMCs of the chemoattractant cytokine, Monocyte Chemoattractant Protein-1 (MCP-1) and of TNF-alpha. Hypotheses generated from these preliminary studies which will be tested in this proposal are: 1)Diisocyanate (DIISO) antigen enhanced production of MCP-1 is a biomarker of DA and validation of the MCP-1 assay as a clinical test will allow differentiation of DA from non-DA; and 2) PBMC production of MCP-1 in response to in vitro stimulation with DIISO antigens correlates with increased secretion of MCP-1 and TNF-alpha in induced BAL fluid of workers with DA as well as with other indices of lung inflammation elicited by workplace exposure to DIISOs. The first aim will be to validate an immunologic assay of in vitro MCP-1 production by PBMCs as a sensitive and specific biomarker of DA. A study will be conducted in recently (less than 6 mo) and remotely (greater than 6 mo) exposed workers to validate the MCP-1 assay using specific bronchial provocation testing with DIISOs (SBPT, currently the diagnostic gold standard) as the active comparitor; DIISO exposed non-asthmatic controls and non-DIISO exposed asthmatics will serve as control groups. The second aim will be to define a relationship between in vitro DIISO enhanced PBMC production and airway inflammation in DA. A second study will evaluate 2 groups of 20 diisocyanate workers with DA and non-DA in whom bronchoalveolar lavage (BAL) will be performed before and 18 hours after diisocyanate inhalation challenge. BAL fluids will be assayed for MCP- l,eotaxin, RANTES, IL-8, TNF-alpha, IL-1, IL-2, IL-4 and IL-5 and BAL cells will be phenotypically characterized and and studied for chemokine and cytokine mRNA expression by in situ hybridization. In vitro antigen enhancement of MCP-1 will be compared by ANOVA for associations with MCP-1 and cytokine levels in BAL fluid. Once validated as a diagnostic biomarker, the MCP- 1 assay can be utilized as a diagnostic method for differentiating workers suspected of DA from those with non-DA or from those individuals with non-occupational asthma.